1. Field of the Invention.
This invention relates to radar systems and, more particularly, to such systems including circuitry for automatically following a selected target.
2. Description of the Prior Art.
Tracking range gates are utilized in radar systems to follow in time coincidence an echo signal reflected from a target. This gating function serves to enhance signal-to-noise ratio and reduce angular tracking error by excluding unwanted targets, noise and other interference which fall outside the time window within which a return pulse from the desired target is anticipated. Although several techniques for automatically tracking the return video signal have been proposed, most of these approaches are costly and complex from the standpoint of the circuits involved. Reference is made to the following prior art systems: U.S. Pat. No. 3,566,405 entitled "Frequency Controlled Range Gate" of L. C. Parode et al; U.S. Pat. No. 3,383,681 entitled "Digital Range Unit" of K. O. Bryant; U.S. Pat. 3,035,263 entitled "Digital Range Tracking Circuit" of L. J. Lader et al; and Canadian Pat. No. 725,810 entitled "Automatic Gating Circuit" of S. P. Applebaum et al.
In addition to its simplicity and reliability, the present invention has a number of other advantages over the prior art. It does not require ramp generators, temperature compensated oscillators, or other precision circuits to effect tracking. Direct range readout is not necessary to initially establish the time position of the gate signal. It will inherently discriminate between targets on the basis of size.
Accordingly, a primary object of the present invention is to provide a simple and reliable traveling range gate circuit capable of automatically locating the return echo and traveling with it as the range of the target varies.